Some engine systems may include devices such as throttle turbine generators to use energy from a pressure difference across a throttle that is otherwise wasted in an intake passage of an engine. In some examples, the throttle turbine generator includes a turbine mechanically coupled to a generator which may generate current that is supplied to a battery of the engine. By charging the battery with such a generator, fuel economy of the engine system may be improved, as compared to charging the battery with an engine driven generator.
In one approach, the throttle blade may have a wedge shape which is thicker at one end than at the opposite end. In such a configuration, airflow to the turbine may be blocked by the edge of the throttle blade during some operating conditions such as during idle conditions, for example. However, such a configuration may reduce airflow to the turbine more than desired under some conditions, thereby reducing a fuel economy benefit of the throttle turbine generator. Further, such a configuration may have an increased risk of freezing or sticking due to the shape of the throttle blade.
The inventors herein have recognized the above problems and have devised an approach to at least partially address them. Thus, a method for an engine is disclosed. In one example, the method comprises, based on airflow to the engine, adjusting a throttle bypass valve to direct at least part of the airflow through a throttle bypass around a throttle disposed in an intake passage of the engine and to a turbine coupled to an auxiliary generator.
In this manner, flow through the throttle bypass may be controlled. For example, when airflow to the engine is relatively low, the bypass valve may be adjusted such that airflow through the bypass is reduced, but not completely reduced in some cases. As another example, when airflow to the engine is relatively high, the bypass valve may be adjusted such that airflow through the bypass is increased. Thus, flow of air through the throttle bypass may be controlled such that the engine receives a desired airflow and fuel consumption is improved under conditions when airflow through the throttle bypass is enough for the turbine to drive the auxiliary generator to charge a battery of the engine.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.